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Data: Goaltender Goal Support (GFA, Goals For Average)

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07-18-2014, 02:00 PM
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Doctor No
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Data: Goaltender Goal Support (GFA, Goals For Average)

Just added a new metric onto my site that I've always had a hard time finding.

I call it GFA (Goals For Average) and I've tried to make it an analogue and direct comparable to GAA (Goals Against Average). It's how many goals of support a goaltender receives per game (per 60 minutes). All of the data come from my game logs data (and so currently only goes back as far as that).

I removed empty net goals scored by the goaltender's team (as well as estimated empty net time).

The one place where I'm not entirely happy with it is in games shared by a goaltender. Ideally (or perhaps not?) if Goaltender A was in net for the first 30 minutes (and his team scored 2 goals) and Goaltender B was in net for the last 30 minutes (and his team scored 0 goals) then Goaltender A would get 2 goals of support and Goaltender B would get 0 goals of support. However, in my game logs, I only have the game-level totals of support.

I'm reasonably happy with this compromise, since ultimately, goal totals only matter at the end of the game (*) and in the grand scheme of things, it doesn't really matter when they were scored during the game. That's somewhat correct and somewhat flawed, of course.

(*) You could also validly argue that goal totals also only matter at the end of the game in relation to the other team's goal totals. That's already measured, although not perfectly, in win-loss records.

Anyhow, these are now on the individual goaltender pages, for instance:
http://hockeygoalies.org/bio/brodeurm.html
http://hockeygoalies.org/bio/roy.html
http://hockeygoalies.org/bio/hasek.html

I'd like to put GFA right next to GAA, since that's the obvious comparable, although GAA is widely accepted while GFA is new so I feel weird doing that just yet.

And on the team-level pages, for instance:
http://www.hockeygoalies.org/bio/nhl/newjersey.html

The team-level pages are perhaps more interesting, since you can compare goaltender (Schneider) vs. goaltender (Brodeur).

Anyhow, enjoy - and comments are welcome (encouraged).

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07-18-2014, 02:14 PM
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One interesting thing I've noticed - Brodeur's win/loss record this past year (relative to Schneider's) is largely related to the massive difference in goal support received by Brodeur (43% more).

Some have argued that (somehow) Brodeur's style of play is the direct cause of this. If that's the case, then I would expect to see it even more when Brodeur was in his prime years, and I'm not seeing a consistent pattern of results in the data.

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07-19-2014, 12:01 AM
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Sitting here staring at Grant Fuhr:
http://hockeygoalies.org/bio/fuhr.html

People always talk about his (relatively) high goals-against averages. The comparable goals-for averages put things in proper perspective.

For instance, Fuhr and the Oilers allowed 3.93 goals per game in 1985-86. How did he go 29-8? It's easy when your team is putting up 5.61 (!) every sixty minutes.

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07-19-2014, 08:31 AM
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Quote:
Originally Posted by Chalupa Batman View Post
The one place where I'm not entirely happy with it is in games shared by a goaltender. Ideally (or perhaps not?) if Goaltender A was in net for the first 30 minutes (and his team scored 2 goals) and Goaltender B was in net for the last 30 minutes (and his team scored 0 goals) then Goaltender A would get 2 goals of support and Goaltender B would get 0 goals of support. However, in my game logs, I only have the game-level totals of support.
I'll pop in for the "or perhaps not" crowd.

When a goalie starts a game he obviously starts it at 0-0. Boiled down, his job is ultimately to allow fewer goals than the goalie across the rink from him. However, when a goalie comes into a game midway through it is rarely 0-0. Unless he's coming in due to injury, his team is generally down multiple goals.

In a way, at the moment of entering the game he's already received -2 or -3 goals of support. His job isn't to simply allow fewer goals, it's to allow 3 or 4 fewer goals.

In the rarer case where a goalie comes in with a lead, he's essentially already received a goal or three of support. Simply because they weren't scored when he was in goal, doesn't mean he doesn't benefit from them.

Granted, I'm not sure how much this would actually affect any analysis, especially for regular starters and they wouldn't come on in relief near as much, however it might be interested to see a GFA for starts only, excluding games where the goalie didn't start the game.

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07-19-2014, 10:24 AM
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That's a really good point - Tom Barrasso allowing 4 goals (in 30 minutes) to start the game is different than Barrasso allowing 4 goals (in 30 minutes) if he comes in with an 8-1 lead.

Ideally, I'd present both (although my "both" philosophy is the primary contributor to the bio pages getting too wide for a single screen ).

I like the GFA in starts idea - that's an easier calculation even, since it's just (totals goals for) / (starts).

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07-19-2014, 09:20 PM
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Quote:
Originally Posted by Chalupa Batman View Post
That's a really good point - Tom Barrasso allowing 4 goals (in 30 minutes) to start the game is different than Barrasso allowing 4 goals (in 30 minutes) if he comes in with an 8-1 lead.

Ideally, I'd present both (although my "both" philosophy is the primary contributor to the bio pages getting too wide for a single screen ).

I like the GFA in starts idea - that's an easier calculation even, since it's just (totals goals for) / (starts).
I think the 'ideal' way to do it would be GFA (calculated like GAA) but only for game starts? This way you remove score effects due to influences from the other goaltender? Though, how often do goalies get pulled and would it really make much difference in the long run?

As an aside... would it be difficult on team pages to flag 'rookie' goalies for seasons, be curious to see if teams tend to have their GF go down for rookie goalies (that's the general wisdom I believe, since they tend to play 'tighter' hockey since they don't expect the kid to come through and bail them out on bad pinches etc).

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07-19-2014, 10:35 PM
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The rookie flags could be done, although I'd probably have to do it manually (set up a table in my database with Calder-eligible seasons, and join it with the main file before exporting).

I do have almost something that could be a good proxy - I have age on the left side of each goaltender's stat line. So for instance:

http://hockeygoalies.org/bio/nhl/ottawa.html

The Senators scored 25% more goals last year for the 32-year-old Anderson than they did for the 22-year-old Lehner, which pretty much explains their W/L differential.

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07-23-2014, 02:22 PM
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I think it is nice to have even a reasonable barometer of how the team is scoring for a particular goaltender.

It really puts some of the goaltender's performances into context.

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07-23-2014, 03:41 PM
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2014 New Jersey Devils:

Brodeur - 41 GP, 2.76 GFA, 2.51 GAA
Schneider - 45 GP, 1.93 GFA, 1.97 GAA

Silly.

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07-23-2014, 03:55 PM
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Quote:
Originally Posted by BraveCanadian View Post
I think it is nice to have even a reasonable barometer of how the team is scoring for a particular goaltender.

It really puts some of the goaltender's performances into context.
Thanks! I realized that I needed it for my predictive model (or rather, the part that wasn't working well was related to future winning percentage, which isn't super important on its own but is correlated to future playing time (since teams certainly think that it's relevant).

Quote:
Originally Posted by AfroThunder396 View Post
2014 New Jersey Devils:

Brodeur - 41 GP, 2.76 GFA, 2.51 GAA
Schneider - 45 GP, 1.93 GFA, 1.97 GAA

Silly.
Agreed - one of my hopes was that the data might show a consistent pattern in Brodeur's GFA, suggesting that he is influencing the team's goal scoring. In his prime years, there *may* be something there, but the problem is that his backups played so few games that it's hard to compare.

In recent years (post-prime) there's no discernible pattern in favor of Brodeur year to year - that could be related to a number of things (in fact, my main conclusion is that in attempting to answer one question, I've introduced a half dozen new questions ).

Some posters (at least one) has suggested that the additional 0.83 goals of support that Brodeur got per game was entirely caused by him, which is a stretch (I'm willing to look at data that shows otherwise).

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